1. Field of the Invention
The present invention relates to a safety scanner, and more particularly, to an improvement of a safety scanner that optically senses an intruder into a protection area.
2. Description of Related Art
An optical safety sensor is an area monitoring device which optically senses an intruder such as a person intruded into a protection area and outputs a safety control signal for emergently stopping a machine such as a machine tool or an industrial robot (e.g., JP 2009-296087 A and JP 2009-294734 A).
For example, a safety scanner is an optical scanning area monitoring device provided with an optical rotator which emits detection light from a light source to a detection area and causes the detection light to perform scanning in the circumferential direction, a light receiving element which receives reflected light from an object within the detection area through the optical rotator and generates a light receiving signal, and an intruder determination section which obtains a distance measurement position corresponding to a distance to the object and a scanning angle of the detection light on the basis of the light receiving signal and compares the distance measurement position with a predetermined protection area to determine the presence or absence of an intruder.
Typically, a safety scanner is provided with a casing which houses a light receiving element and an intruder determination section, and a protective cover for protecting an optical rotator. For example, in a safety scanner that covers an optical rotator with a U-shaped metal casing and a protective cover, the protective cover is attached to the metal casing from the front side thereof. Further, maintenance of the optical rotator and the like is required or the protective cover is required to be replaced when damaged. Thus, the protective cover is required to be detachably attached to the metal casing.
In a conventional safety scanner, the cross section of the protective cover taken along a plane perpendicular to a rotation axis of the optical rotator is formed in a circular arc shape on the front side with respect to the rotation axis and in a linear shape on the rear side with respect to the rotation axis to ensure the view angle of 180° or more. Thus, the curvature of the protective cover differs between the front side and the rear side with respect to the rotation axis, which disadvantageously changes the optical performance depending on a scanning angle of detection light.
In a safety scanner that covers an optical rotator only with a protective cover, the protective cover is attached to a lower casing from the upper side. Thus, the above technical problem does not occur.